For the detection of radiation, many different types of detectors are known from the prior art. For sensing high energy electromagnetic radiation, scintillation detectors comprising a scintillator crystal and a photomultiplier tube are widely used in different technical fields, e.g. in medical imaging equipment or for well-logging in the oil and gas industry. In a scintillation detector, the radiation falls on a scintillator crystal converting the radiation in light impinging on a photocathode. This photocathode is part of a photomultiplier tube comprising a plurality of dynodes in a glass envelope. Due to the photoelectric effect, the light falling on the photocathode causes the emission of primary electrons inside the photomultiplier tube. The electrons are accelerated towards the dynodes in the tube resulting in secondary electron cascades which are detected as an output signal. Scintillation detectors are relatively bulky due to the photomultiplier tube which has a length of several centimeters. Furthermore, the spatial resolution of those detectors is relatively low.
Another type of detector known from the prior art refers to so-called gas electron multipliers where electrons generated by the photoelectric effect enter corresponding holes filled with gas. There is a high electric field within the holes accelerating the electrons entering the holes resulting in secondary electrons due to the hits of the electrons with gas atoms/molecules. Thus, an electron avalanche is generated.
A radiation detector including a gas electron multiplier is disclosed in U.S. Pat. No. 6,011,265. In this detector, a detector anode arranged in a distance from the gas electron multiplier is used for detecting the electron avalanche. The gas electron multiplier comprises an insulating material with corresponding holes therein and two electrodes disposed on the insulating material which generate a high electric field inside the holes. The detector has the disadvantage that not all electrons of the electron avalanche can be detected by the detector anode because some electrons are discharged on the electrode of the gas electron multiplier adjacent to the detector anode.